EGF and CSF-1 are the key growth factors involved in signaling of macrophages and carcinoma cells to result in chemotaxis and invasion. Little is know about mechanisms of chemotaxis in either cell type. Activation of Class I (p85/p110) PI 3-kinases are essential proximal effectors of motility in both carcinoma cells and macrophages. However, EGF-stimulated motility in carcinoma cells specifically requires p85/p110a, whereas CSF-1 stimulated motility in macrophages requires p85/p110b and p85/p110d. Beyond this observation, PI 3-kinase activation and signaling in these lines has not been carefully compared. Differences in PI3K signaling pathways may distinguish invasion by macrophages and carcinoma cells at the molecular level. Cofilin and Arp2/3 complex are terminal effectors in the actin cytoskeleton connecting EGF to leading edge assembly and cell motility in carcinoma cells. Capping protein may play a similar role to cofilin during CSF-1 stimulation of motility in macrophages. EGF and CSF-1 stimulated signaling pathways are hypothesized to occur through the different branches of the actin polymerization pathway involving either cofilin or capping protein, respectively, and ending in a common downstream step involving Arp2/3 complex. Different WASP/WAVE family members are believed to mediate signaling in macrophages and carcinoma cells. In this project we will study signaling from EGF and CSF-1 receptors to PI3K and effectors in the actin cytoskeleton that define leading edge assembly and chemotaxis. By understanding these signaling pathways in macrophages and carcinoma cells and comparing and contrasting them, it will be possible to determine if cell type specific inhibition of chemotaxis will be possible leading to potential cytostatic therapies to inhibit invasion.